Extracts obtainable from plants of the Asclepiadaceae family, particularly the Hoodia genus (formerly the Hoodia and Trichocaulon genera) have been shown to have an appetite suppressant activity. U.S. Pat. No. 6,376,657 discloses that these plants contain steroidal glycosides having the formula 1:
whereinR=alkyl;R1═H, alkyl, tiglyol, benzoyl or any other organic ester group;R2═H or one or more 6-deoxy carbohydrates, or one or more 2,6-dideoxy carbohydrates, or glucose radical or combinations thereof; and wherein the broken lines indicate the optional presence of a further bond between carbon atoms C4 and C5 or between carbon atoms C5 and C6.
U.S. Pat. No. 6,376,657 also discloses processes to extract steroidal glycosides having the formula 1 from Hoodia plants, involving treating plant material with a solvent to extract a fraction having appetite suppressant activity, separating the extraction solution from the rest of the plant material, removing the solvent from the extraction solution, optionally treating the solution with the additional solvent, and recovering the extract. The solvents specifically disclosed include methylene chloride, also known as dichloromethane. The patent also discloses methods for synthesizing various steroidal glycosides.
U.S. Pat. No. 7,060,308 (Rajendran et al.) discloses Caralluma extracts. U.S. Pat. No. 7,008,648 (Corley et al.) discloses extracts obtainable from plants of the Stapelia and Orbea genera. WO 2005/099737 (Rutgers University) also discloses extracts and processes of obtaining extracts from Asclepias plants.
WO2005/116049 (Unilever) discloses that steroidal glycosides can be extracted or separated from undesirable components present in plant material of the Asclepiadaceae family by means of liquid or supercritical carbon dioxide.
The need remains for alternate processes of preparing Hoodia extracts, resulting in a high content of steroidal glycosides and suitable for use in foods (e.g. the use of chlorinated solvents is undesirable).
Depending on the origin of the plant materials, they may contain traces of heavy metals like copper or zinc and polyaromatic hydrocarbons (PAH) which may be enriched during the extraction processes. Thus, there is also a need for processes which attain extracts with minimised heavy metal and PAH content.
Therefore, the object of the present invention is to develop a manufacturing process for obtaining a Hoodia plant extract with a high content of steroidal glycosides and which uses food grade solvents.
Yet another object of the present invention is to obtain by-products like water-soluble short-chain active principles, long-chain waxes and fatty acids from Hoodia plants in a purity which allows using them for other purposes in order to make the process even more economic.
Still another object of the invention is to develop a manufacturing process for obtaining Hoodia extracts with minimised heavy metal and/or PAH content.